Treesearch

Climate change, population growth, urbanization, and interactions thereof may alter the water supply-demand balance and lead to shifts in water shortage characteristics at different timescales. This study proposes an approach to improve the vulnerability assessments of U.S. river basins to the shortage at the interannual to decadal timescales by characterizing shifts in intensity, duration, and frequency (IDF) of water shortage events from current (1986-2015) to future (2070-2099) periods. The results indicate that under the driest future climate projection, the frequency and intensity of...

Nearctic-Neotropical migratory birds are considered priority species for conservation because they are subject to threats at distinct breeding, migratory and stopover locations throughout their annual cycle, and many species have undergone severe population declines. Research during the non-breeding season has focused on identifying the locations and habitats that migrants use, but wintering migrants are known to occupy habitats of both high and low quality, especially when the best sites are saturated by conspecifics. Thus, the presence or abundance of a species may not be a reliable...

Wildfire has become a larger threat to human life and property with the proliferation of homes into the wildland urban interface and warming climate. In this study we explored Alaskan homeowner preferences for wildfire risk mitigation in the wildland urban interface using discrete choice experiments to better understand the drivers of their risk mitigation actions. Estimates of willingness-to-pay for private mitigation actions are increased with wildfire risk reduction for all respondents. Willingness-to-pay for private mitigation is also positively associated with the presence of thinned...

A key component in understanding plant-insect interactions is the nature of host defenses. Research on defense traits among Pinus species has focused on specialized metabolites and axial resin ducts, but the role of lignin in defense within diverse systems is unclear. We investigated lignin levels in the outer bark and phloem of P. longaeva, P. balfouriana, and P. flexilis; tree species growing at high elevations in the western United States known to differ in susceptibility to mountain pine beetle (Dendroctonus ponderosae; MPB). Pinus longaeva and P. balfouriana are attacked by MPB less...

Catalytic pathways to produce high carbon number compounds from benzyl phenyl ether require multiple steps to break the aryl etheric carbon–oxygen bonds; these steps are followed by energy-intensive processes to remove oxygen atoms and/or carbon–carbon coupling. Here, we show an upgrading strategy to transform benzyl phenyl ether into large phenolic (C12–C22) compounds by a one-step C–O breaking and C–C coupling catalyzed by metal triflates under a mild condition (100 °C and 1 bar). Hafnium triflate was the most selective for the desired products. In addition, we measured the effect of...

1. Wildfire can both promote and erode resilience to future disturbances in fire-adapted ecosystems. Through a combination of past fire exclusion and climate change, fire patterns and successional trajectories are shifting with potentially negative consequences for forest resilience. In particular, high-severity short-interval reburns can lead to permanent transitions from forested to persistent non-forested ecosystems. 2. To test conditions under which wildfires promote resilience or initiate vegetation transitions we leveraged high-resolution LiDAR data, field data and a natural experimen...

Background Fire suppression in western North America increased and homogenized overstory cover in conifer forests, which likely affected understory plant communities. We sought to characterize understory plant communities and their drivers using plot-based observations from two contemporary reference sites in the Sierra Nevada, USA. These sites had long-established natural fire programs, which have resulted in restored natural fire regimes. In this study, we investigated how pyrodiversity—the diversity of fire size, severity, season, and frequency—and other environment factors influenced...

The overwhelming majority of information on historical forest conditions in western North America comes from public lands, which may provide an incomplete description of historical landscapes. In this study we made use of an archive containing extensive timber survey data collected in the early 1920s from privately owned forestland. These data covered over 50,000 ha and effectively represent a 19% sample of the entire area. The historical forest conditions reconstructed from these data fit the classic model of frequent-fire forests: large trees, low density, and pine-dominated. However,...

Surface fuel loads are highly variable in many wildland settings, which can have many important ecological effects, especially during a wildland fire. This variability is not well described by a single metric (e.g. mean load), so quantifying traits such as variability, continuity and spatial arrangement will help more precisely describe surface fuels. This study measured surface fuel variability in the northern Sierra Nevada of California following a high-severity fire that converted a mixed-conifer forest to shrub-dominant vegetation, both before and after a subsequent shrub removal...

Increased nitrogen (N) deposition may have profound effects on forest ecosystems. However, information on the impacts of elevated N deposition on belowground soil seed bank in forests is lacking. In a field experiment, we added N at 50 and 25 kg N ha−1 year−1 to the canopy (CAN50 and CAN25) and to the understory (UAN50 and UAN25), to determine the effects of N deposition on soil seed bank structure and composition in a subtropical evergreen broadleaved forest. A total of 1545 seedlings belonging to 37 species emerged from the 10 cm-depth soil samples. After 6 years of N addition, soil seed...